Orthopedic devices, such as braces, are periodically rejected due to the tendency of muscles weakening because of wearer over reliance of the brace. This phenomenon occurs when the brace immobilizes the target condition it should treat, such as osteoarthritis, by delaying eventual recovery. The wearer may become more reliant on the brace for support and less reliant on the actual muscles for stabilizing the joint.
In the example, osteoarthritis is a progressive degenerative joint disease that often results in disability and a loss of joint function. Osteoarthritis of the knee may be debilitating since the knee is stressed from daily activities, such as walking up and down stairs, or even when resting. Osteoarthritis causes a gradual breakdown of the cartilage in the joints. As the disease progresses and cartilage wears away, the bones rub and grind against each other cause pain.
Knee osteoarthritis is a chronic degenerative condition in that it gradually worsens. In the early stages of development, people often cut back on their activities or work because of discomfort and pain. Advanced knee osteoarthritis is associated with pain, stiffness and inflammation.
In a healthy knee, cartilage covers the ends of the bones and prevents them from rubbing against each other. As the surface of the cartilage breaks down, small cracks and indentations may form. In a mild case of osteoarthritis, the knee might show signs of varus misalignment. Over time, sections of cartilage wear down, reducing flexibility and increasing the likelihood of becoming damaged by daily activities. The lubricating fluid (synovial fluid) breaks down and become less effective, while cracks and pits continue to appear in cartilage. As the knee degenerates, the leg develops a bowed appearance.
In severe osteoarthritis, bones are left unprotected as large sections of the cartilage are worn away, resulting in pain from bones grating against each other as they move. Pain and damage may arise from small fragments of cartilage that have become detached and may be floating around the joint. Externally, the leg will often appear severely bowed in relation to the thigh.
Many braces used to address osteoarthritis immobilize the knee and take up some muscle function used otherwise by the user's muscles. These braces can often eliminate or postpone the need for surgery, and have none of the effects of pain-relief medication. The braces have a tendency to replace or minimize quadriceps function. Quadriceps weakness, however, is also a cause for development of osteoarthritis of the knee and is one of the issues that a physical therapist attempts to rehabilitate when treating a user with osteoarthritis of the knee. By treating the knee with a brace, improvement of muscle weakness is inhibited and the user is unable fully recover muscle strength.
As well understood, the quadriceps muscles are the muscles in the anterior surface of the thigh, and include four separate muscles groups: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Quadriceps weakness is commonly associated with osteoarthritis of the knee is widely believed to result from disuse atrophy secondary to pain in the involved joint. Quadriceps weakness is a primary risk factor for knee pain, disability, and progression of joint damage in persons with osteoarthritis of the knee.
Studies have shown regular, moderate exercise is also beneficial to arthritis sufferers. It helps keep the joints flexible and increases the range of motion. When one exercises, the body releases endorphins, which are natural painkillers. It is therefore advantageous not only to use and strengthen the muscles, but moderate usage of the muscles can improve the condition of osteoarthritis sufferers.
It has been found that certain orthopedic devices provide dynamic strengthening of muscle groups when stabilizing a joint. A dynamic osteoarthritis knee brace (“OA brace”) includes straps arranged to load muscle groups between extension and flexion during gait, as described in U.S. Pat. No. 7,198,610, issued on Apr. 3, 2007 and incorporated by reference. In the OA brace, force straps exert a load on the quadriceps through dynamic extension resistance while unloading compartments of the knee to provide correct joint orientation.
FIGS. 1A and 1B exemplify known OA braces having one or more force straps. In FIG. 1A, the OA brace employs a medial upright with a valgus bend plus an opposing dynamic force strap to generate a three-point leverage system that unloads the medial compartment of the knee. The quadriceps resist the load as the knee goes into extension actively allowing for some quadriceps use to maintain some strength of the leg while wearing a brace.
FIG. 1B shows a similar three-point leverage system by including a flexible upright and including dual dynamic force straps to disperse the counter force that the quadriceps resist across two points of contact. The force on the knee is arranged to reduce the pressure on the affected part of the knee, resulting in reduction in pain, and allowing the patient to use the knee normally and more frequently.
Some users wearing the aforementioned OA braces may not understand when to activate the quadriceps during a gait cycle, particularly at certain points, or they may require additional muscle strengthening at the quadriceps or other areas such as the gluteus medius to assure better corrective therapy for treating osteoarthritis of the knee.
As discussed herein, electrical stimulation may be of the type commonly referred to as Transcutaneous Electrical Nerve Stimulation (TENS) used primarily as a pain blocker by creating a buzzing sensation that blocks a pain signal from the nerve where it is perceived in the brain as pain. Electrical Muscle Stimulation or Neuromuscular Electrical Stimulation (NMES) is used to affect the muscle by targeting it to prevent retardation or muscular disuse atrophy, and provide relaxation of muscle spasms, muscle reeducation, blood circulation and activation. The intensity of either TENS or NMES may be modified accordingly to increase cocontraction.
TENS and NMES are interchangeably referred to herein to as “electrical stimulation,” with the recognition that the type of stimulation may vary according to its particular application (i.e., pain blocking or muscle activation, respectively).
NMES is the elicitation of muscle contraction using electric impulses and has received increasing attention in the last few years because it has the potential to serve as: a strength training tool; a rehabilitation and preventive tool for partially or totally immobilized patients; a testing tool for evaluating the neural and/or muscular function in vivo; and a post-exercise recovery tool for individuals. The impulses are generated by a device and delivered through electrodes on the skin in direct proximity to the muscles to be stimulated. The impulses mimic the action potential coming from the central nervous system, causing the muscles to contract.